Guest Post: Yuki Learns You Stat Weighting (p3)

June 25, 2009

As stated last week, here’s the post outlining how to determine weights to plug into lootrank to figure out your best in slot. It’s a general list written by (alas) a DPS-type, so it’s not aimed at healers specifically, but I hope you all can still find it useful. Yuki’s been my guildie, my buddy, and enabler of my anime addiction for several years now. He’s also the first person who told me that such a thing as mathcraft exists. Be warned, there’s numbers ahead.

Step 5: Final Complications

There are basically two things left that haven’t been modeled. The first is mana regen, which creates some difficulties, and the second is trinkets and the like with activated or proc effects, which presents others.

5a: Mana Regen

The main thing about mana regen is that it only matters if you run out of mana. This can make it hard to model, since it’s not something that easily converts directly into spellpower or attack power.

Probably the most common way of modeling mana regen is in terms of how many extra spells it lets you cast if you WERE to cast until you ran out. Basically, you figure out how long you can cast without running out of mana, and how much effective healing or damage you’d do on average. Then you see how much 1mp5 would let you cast. You compare how much a point of spell damage would have added vs. the amount the mp5 added to determine the effective spellpower value of a point of mp5. This is a popular method because it’s pretty straightforward, and you can modify it a little to include out of 5 second rule regen if you’d like.

Another method is to work backwards: essentially, you take a length of time longer than the amount of time it would take you to run out of mana chain casting and then calculate how much less time you have to spend on 5-second-rule regen to determine how many more spells you could cast, and use that to derive the relative value.

As you can probably guess, there really isn’t a great way to graft mp5 onto spellpower. Still, these two methods at least produce something, which can be modestly useful for modeling gear.

5b: Procs

So, we’ve basically covered how to model static stats; what about ones that aren’t so static? Generally these are in the form of either active abilities (clicky trinkets, for instance) or passive procs (chance-on-hit/crit trinkets). How to model these?

Actives are actually pretty easy. You can basically model them as “permanent” power by dividing their effect by the amount of time it spends on cooldown. So, for instance, a trinket that provides 200 spellpower for 15 seconds on a 1 minute cooldown is effectively the same as one that grants 50 spellpower all the time. This isn’t wholly accurate (since you can stack some cooldowns to get more out of them, like an unholy DK blowing Gargoyle while her trinket buffs are up), but it’s good enough for government work.

Passives are trickier. You need to know the proc rate and internal cooldown, which are almost never listed; you’ll need to get them from datamining or testing. Use these to calculate the average uptime % (which is the proc duration divided by average time to proc + internal cooldown), then multiply the value of the proc by that. Since this requires you to use the average time to proc, which can vary wildly for low-chance trinkets, and it shares the flaw of not modeling stacked-burst very well with the active version, it’s not wholly accurate, but it gets the job done well enough to compare trinkets.

Step 6: Putting it all together

At this stage, you have enough information to generate final stat weights: for each overall stat, add up the weights you calculated for each of their effective ratings you calculated above to determine the final overall weight of that stat. So, for instance, the value of a point of int is:

I used Int on purpose, because an observant reader will note that it provides a benefit we haven’t modeled: an increase to your base mana pool. You’ll have to determine what weight (if any) you give to that similarly to how you chose to calculate mp5; I didn’t mention it there mostly so that I could point out that at this stage you should be on the look out for stat effects that you hadn’t considered yet!

Once you’ve done this for everything, you’ll have your final weights for stats as calculated against your baseline! Now you can use them to help consider gear . . . until you move too far away from your baseline and have to recalculate them.

Closing Thoughts

I’ve always been fairly skeptical of stat weights as anything other than very general comparisons of how “strong” a given stat is. Having seen this demonstration of what hot dogs are made up, you can probably see why: there’s a lot of assumptions in the process, and the end result loses value considerably as you move away from your baseline. I tend to agree with Ghostcrawler’s assessment that if you’re just pulling “best” gear from somewhere based on this stuff, you’re not necessarily doing yourself a service as it won’t necessarily actually be “best” for you if your gear is different than the assumptions.

One thing this process will teach you, though, is the underlying mechanics of your class, including what scales with what and how things interact, which is probably the most important thing to learn for any form of theorycraft. The numbers generated may be of limited value, but the process of generating them has some fairly valuable lessons to be learned along the way.

Aaand done! You’ve made it! Special huge thanks to Yuki for putting this together and trying to learn us some math. Did it work for you?

Also, there’s not gonna be a Tuesday post for me next week. I’m currently in California visiting my family with the Tarsus; and my mom doesn’t really live in this century as far as internet goes. But I’ll catch you all the next week!

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9 comments

Fantastic conclusion. There is little I can add to that ;)

I do wonder about regen. As you mention it only matters if you run out, perhaps a primitive but effective method is calculating the MPS of your spellcycle and have that measure against your regen/time and manabar. On a spreadsheet, that’s 10s work. It’s not the most effective to weigh stats but at least it’s easy to approximate how long your mana will last.

One more thing: as far as the trinkets and proc effects is concerned, there are pretty standard methods to model/estimate those. Wowhead typically reveals the internal cooldown and procrate, which is all you need.

That’d be a good way to estimate the duration of your mana bar, yes. In fact it’s probably more or less how I’d do it, since to be frank it’s already way off in abstractland and it’s probably not going to be too terribly far off from simulating the rotation for ages until it can’t go on anymore.

That’s a pretty nice tool, tool :) And yes, you can often find the answer to what the ICD/proc rate are by searching, as someone else has probably done it before; I described the process the way I did primarily for pedagogical reasons, since the question upon reading “find the values” is immediately “how are they derived?” :D

“I tend to agree with Ghostcrawler’s assessment that if you’re just pulling “best” gear from somewhere based on this stuff, you’re not necessarily doing yourself a service as it won’t necessarily actually be “best” for you if your gear is different than the assumptions.”

This in practice is not correct. Due to the very limited pool of gear at the top item levels, if you use any sensible stat weighting you will come to the same conclusion. That is that gear with higher gear level is almost always better.

Sure your best-in-slot item might be number two or three on someone elses list, but the differences are fairly minor and you certainly won’t be doing yourself a disservice by using it.

That’s simply not true. Higher iLevel = more points to spend on stats, but there’s a lot of exceptionally poorly itemized gear in the game, and even well itemized gear isn’t always an upgrade over your lower iLevel stuff if your old stuff has stats on it that you need while the newer gear has stats that you don’t.

The problem is perhaps more pronounced for DPS than for healers (since there are stats that start extremely valuable and become completely worthless beyond a certain threshold), but it’s still true that if, say, you’re a healdin and you’re taking higher iLevel mp5 gear, you’re not going to heal as well as another healdin who’s wearing tier-behind crit plate.

iLevel is all well and good, but if it’s your only touchstone you’re going to end up behind. It may be true that a given piece is BiS in the context of all the other BiS gear, but there’s no guarantee at all that the piece is actually better for you in the context of your existing gear.

I think both score a point here. Bob and I have both examined lists and priorities (well, he did the real work & I just criticized it lol). Even if your balance of stats changes it doesn’t necessarily yield a big difference in the loot ranks. At least not in the top 3 (since there seems to be less choice at high iLvls). Once you aim for 2-3 stats to be important, a list with those 2-3 stats will be returned and tho one item may score a few points higher or lower depending on the weights… this doesn’t necessarily change their position.

However, I agree with Yuki that a distinction for healers and dps must be made. Healers are reactive, situational and thus each stat does not directly contribute its potential. I was able to outheal far better geared players before and I’ve seen lower geared players keep up with me. The reason being we are, at any point, healing capped. The battle is then not ‘how much healing you can produce’ but how the healing that must be done is divided. I do expect this contrast to diminish in hardmodes where all healers get pushed to their limits.

@yuki – I must admit i’m thinking of healing priests more than general gear lists (sometimes I forget there are others playing ;-) ). The healing priest gear is pretty standard fare and itemisation comes down to likeing either more or less spirit and haste vs crit.

re: your healdin example, unless they are wearing a lot of MP5 gear and have unusually low crit then taking the higher ilvl gear isn’t going to significantly effect performance.

I haven’t looked at the itemisation of T8+ healdin gear but i’d be surprised if it was full of gear with MP5 and little crit rating.